Cutting tool

ABSTRACT

A cutting tool including a rake face, a flank face, and a cutting edge portion, comprising a substrate and an AlTiN layer, the AlTiN layer including cubic AlxTi1-xN crystal grains, Al having an atomic ratio x of 0.7 or more and less than 0.95, the AlTiN layer including a central portion, the central portion at the rake face being occupied in area by (111) oriented AlxTi1-xN crystal grains at a ratio of 50% or more and less than 80%, the central portion at the cutting edge portion being occupied in area by (111) oriented AlxTi1-xN crystal grains at a ratio of 80% or more.

TECHNICAL FIELD

The present disclosure relates to a cutting tool. The presentapplication claims priority based on Japanese Patent Application No.2019-078671 filed on Apr. 17, 2019. All contents described in theJapanese patent application are incorporated herein by reference.

BACKGROUND ART

Conventionally, cutting tools made of cemented carbide or cubic boronnitride sintered material (cBN sintered material) have been used to cutsteel and castings. In a cutting process, such cutting tools have theircutting edges exposed to a harsh environment such as high temperatureand high stress, which invites wearing and chipping of the cutting edge.

Accordingly, suppressing the wearing and chipping of the cutting edge isimportant in improving the cutting performance of the cutting tool andhence extending the life of the cutting tool.

In order to improve a cutting tool in cutting performance (e.g.,breaking resistance, crater wear resistance and flank wear resistance),a coating which coats a surface of a substrate of cemented carbide, acBN sintered material and the like has been developed. Inter alia, acoating composed of a compound of aluminum (Al), titanium (Ti) andnitrogen (N) (hereinafter also referred to as “AITiN”) can have highhardness and also enhance oxidation resistance. (For example seeJapanese Patent Laying-Open Nos. 9-295204 (PTL 1), 9-300106 (PTL 2), and10-330914 (PTL 3)).

CITATION LIST Patent Literature

PTL 1: Japanese Patent Laid-Open No. 9-295204

PTL 2: Japanese Patent Laid-Open No. 9-300106

PTL 3: Japanese Patent Laid-Open No. 10-330914

SUMMARY OF INVENTION

The presently disclosed cutting tool is

a cutting tool including a rake face, a flank face, and a cutting edgeportion connecting the rake face and the flank face together,

the cutting tool comprising a substrate and an AlTiN layer provided onthe substrate,

the AlTiN layer including cubic Al_(x)Ti_(1-x)N crystal grains,

an atomic ratio x of Al in the Al_(x)Ti_(1-x)N being 0.7 or more andless than 0.95,

the AlTiN layer including a central portion,

the central portion being a region sandwiched between an imaginary planeD and an imaginary plane E, the imaginary plane D being an imaginaryplane which passes through a point 1 μm away in a direction of thicknessfrom a first interface located on a side of the substrate and isparallel to the first interface, the imaginary plane E being animaginary plane which passes through a point 1 μm away from a secondinterface opposite to the side of the substrate in the direction ofthickness and is parallel to the second interface,

the first interface being parallel to the second interface,

when a cross section of the AlTiN layer obtained when cut along a planeincluding a normal to the second interface at the rake face and a normalto the second interface at the flank face is subjected to an electronbackscattering diffraction image analysis using a field emissionscanning microscope to determine a crystal orientation of each of theAl_(x)Ti_(1-x)N crystal grains and a color map is created based thereon,

then, in the color map,

the central portion at the rake face being occupied in area at a ratioof 50% or more and less than 80% by Al_(x)Ti_(1-x)N crystal grainshaving a (111) plane with a normal thereto having a direction within±15° with respect to a direction of the normal to the second interfaceat the rake face,

the central portion at the cutting edge portion being occupied in areaat a ratio of 80% or more by Al_(x)Ti_(1-x)N crystal grains having the(111) plane with a normal thereto having a direction within ±15° withrespect to a direction of a normal to the cutting edge portion,

the direction of the normal to the cutting edge portion being adirection of a normal to an imaginary plane C including a boundary lineon the substrate between the rake face and the cutting edge portion anda boundary line on the substrate between the flank face and the cuttingedge portion.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view for illustrating one embodiment of acutting tool.

FIG. 2 is a cross section taken along a line X-X indicated in FIG. 1.

FIG. 3 is a partial enlarged view of FIG. 2.

FIG. 4 is a cross section of a cutting edge portion having another shapeby way of example.

FIG. 5 is a cross section of the cutting edge portion having stillanother shape by way of example.

FIG. 6 is a schematic cross section of one embodiment of the cuttingtool by way of example.

FIG. 7 is a schematic cross section of another embodiment of the cuttingtool by way of example.

FIG. 8 is a schematic cross section of still another embodiment of thecutting tool by way of example.

FIG. 9 is a schematic representation of a color map created based on across section of an AlTiN layer.

FIG. 10 is a schematic cross section of a CVD apparatus used formanufacturing the cutting tool according to the present embodiment.

FIG. 11 is a schematic cross section of a gas introduction pipe of theCVD apparatus used in manufacturing the cutting tool according to thepresent embodiment.

DETAILED DESCRIPTION Problems to be Solved by the Present Disclosure

In recent years, more efficient (or higher feed rate) cutting processinghas been demanded, and further improvement is expected in wearresistance (or further suppression of wearing) of a flank face of acutting tool used for processing high-hardness materials (for example,SKD material).

The present disclosure has been made in view of the above circumstances,and an object thereof is to provide a cutting tool having excellentflank wear resistance.

Advantageous Effect of the Present Disclosure

According to the present disclosure, a cutting tool having excellentflank wear resistance can be provided.

Description of Embodiment of the Present Disclosure

First, embodiments of the present disclosure will be listed anddescribed.

[1] The presently disclosed cutting tool includes

a cutting tool including a rake face, a flank face, and a cutting edgeportion connecting the rake face and the flank face together,

the cutting tool comprising a substrate and an AlTiN layer provided onthe substrate,

the AlTiN layer including cubic Al_(x)Ti_(1-x)N crystal grains,

the atomic ratio x of Al in the Al_(x)Ti_(1-x)N being 0.7 or more andless than 0.95,

the AlTiN layer including a central portion,

the central portion being a region sandwiched between an imaginary planeD and an imaginary plane E, the imaginary plane D being an imaginaryplane which passes through a point 1 μm away in a direction of thicknessfrom a first interface located on a side of the substrate and isparallel to the first interface, the imaginary plane E being animaginary plane which passes through a point 1 μm away from a secondinterface opposite to the side of the substrate in the direction ofthickness and is parallel to the second interface,

the first interface being parallel to the second interface,

when a cross section of the AlTiN layer obtained when cut along a planeincluding a normal to the second interface at the rake face and a normalto the second interface at the flank face is subjected to an electronbackscattering diffraction image analysis using a field emissionscanning microscope to determine a crystal orientation of each of theAl_(x)Ti_(1-x)N crystal grains and a color map is created based thereon,

then, in the color map,

the central portion at the rake face being occupied in area at a ratioof 50% or more and less than 80% by Al_(x)Ti_(1-x)N crystal grainshaving a (111) plane with a normal thereto having a direction within±15° with respect to the direction of the normal to the second interfaceat the rake face,

the central portion at the cutting edge portion being occupied in areaat a ratio of 80% or more by AlTiN crystal grains having the (111) planewith a normal thereto having a direction within ±15° with respect to adirection of a normal to the cutting edge portion,

the direction of the normal to the cutting edge portion being adirection of a normal to an imaginary plane C including a boundary lineon the substrate between the rake face and the cutting edge portion anda boundary line on the substrate between the flank face and the cuttingedge portion.

The above cutting tool thus configured has excellent flank wearresistance. As used herein, “flank wear resistance” means resistance towear on a flank face.

[2] The AlTiN layer has a thickness of 2.5 μm or more and 20 μm or less.By defining in this way, the cutting tool can be further excellent inflank wear resistance.

[3] The cutting tool further includes an underlying layer providedbetween the substrate and the AlTiN layer, and

the underlying layer is composed of a compound consisting of: at leastone element selected from the group consisting of a group 4 element, agroup 5 element and a group 6 element of the periodic table andaluminum; and at least one element selected from the group consisting ofcarbon, nitrogen, oxygen and boron. By defining in this way, the cuttingtool can have flank wear resistance and, in addition thereto, the AlTiNlayer with excellent peel resistance.

[4] The cutting tool further includes a surface layer provided on theAlTiN layer, and

the surface layer is composed of a compound consisting of: at least oneelement selected from the group consisting of a group 4 element, a group5 element and a group 6 element of the periodic table and aluminum; andat least one element selected from the group consisting of carbon,nitrogen, oxygen and boron. By defining in this way, the cutting toolcan be further excellent in flank wear resistance.

Details of Embodiments of the Present Disclosure

Hereinafter, an embodiment of the present disclosure (hereinafter alsoreferred to as “the present embodiment”) will be described. It should benoted, however, that the present embodiment is not exclusive. In thepresent specification, an expression in the form of “X to Y” means arange's upper and lower limits (that is, X or more and Y or less), andwhen X is not accompanied by any unit and Y is alone accompanied by aunit, X has the same unit as Y. Further, in the present specification,when a compound is represented by a chemical formula with itsconstituent elements having a composition ratio unspecified, such as“TiN,” the chemical formula shall encompass any conventionally knowncomposition ratio (or elemental ratio). The chemical formula shallinclude not only a stoichiometric composition but also anonstoichiometric composition. For example, the chemical formula of“TiN” includes not only a stoichiometric composition of “Ti₁N₁” but alsoa non-stoichiometric composition for example of “Ti₁N_(0.8).” This alsoapplies to descriptions for compounds other than “TiN.”

<<Surface-Coated Cutting Tool>>

The presently disclosed cutting tool is

a cutting tool including a rake face, a flank face, and a cutting edgeportion connecting the rake face and the flank face together,

the cutting tool comprising a substrate and an AlTiN layer provided onthe substrate,

the AlTiN layer including cubic Al_(x)Ti_(1-x)N crystal grains,

the atomic ratio x of Al in the Al_(x)Ti_(1-x)N being 0.7 or more andless than 0.95,

the AlTiN layer including a central portion,

the central portion being a region sandwiched between an imaginary planeD and an imaginary plane E, the imaginary plane D being an imaginaryplane which passes through a point 1 μm away in a direction of thicknessfrom a first interface located on a side of the substrate and isparallel to the first interface, the imaginary plane E being animaginary plane which passes through a point 1 μm away from a secondinterface opposite to the side of the substrate in the direction ofthickness and is parallel to the second interface,

the first interface being parallel to the second interface,

when a cross section of the AlTiN layer obtained when cut along a planeincluding a normal to the second interface at the rake face and a normalto the second interface at the flank face is subjected to an electronbackscattering diffraction image analysis using a field emissionscanning microscope to determine a crystal orientation of each of theAl_(x)Ti_(1-x)N crystal grains and a color map is created based thereon,

then, in the color map,

the central portion at the rake face being occupied in area at a ratioof 50% or more and less than 80% by Al_(x)Ti_(1-x)N crystal grainshaving a (111) plane with a normal thereto having a direction within±15° with respect to the direction of the normal to the second interfaceat the rake face,

the central portion at the cutting edge portion being occupied in areaat a ratio of 80% or more by Al_(x)Ti_(1-x)N crystal grains having the(111) plane with a normal thereto having a direction within ±15° withrespect to a direction of a normal to the cutting edge portion,

the direction of the normal to the cutting edge portion being adirection of a normal to an imaginary plane C including a boundary lineon the substrate between the rake face and the cutting edge portion anda boundary line on the substrate between the flank face and the cuttingedge portion.

In the present embodiment, being “parallel” is a concept including notonly being geometrically parallel but also being generally parallel.

A surface-coated cutting tool (hereinafter also simply referred to as a“cutting tool”) 1 of the present embodiment includes a substrate 10, andan AlTiN layer 11 provided on substrate 10 (For example, see FIG. 6). Inaddition to AlTiN layer 11, cutting tool 1 may further include anunderlying layer 12 provided between substrate 10 and AlTiN layer 11(see FIG. 7). Cutting tool 1 may further include a surface layer 13provided on AlTiN layer 11 (see FIG. 8). Other layers such as underlyinglayer 12 and surface layer 13 will be described hereinafter.

The above-described layers provided on substrate 10 may be collectivelyreferred to as a “coating.” That is, cutting tool 1 includes a coating14 provided on substrate 10, and the coating includes AlTiN layer 11.Further, coating 14 may further include underlying layer 12 or surfacelayer 13.

The cutting tool can for example be a drill, an end mill (e.g., a ballend mill), an indexable cutting insert for a drill, an indexable cuttinginsert for an end mill, an indexable cutting insert for milling, anindexable cutting insert for turning, a metal saw, a gear cutting tool,a reamer, a tap, or the like.

The cutting tool includes a rake face, a flank face, and a cutting edgeportion connecting the rake face and the flank face. A “rake face” meansa face ejecting chips produced from a workpiece as it is cut. A “flankface” means a face partially brought into contact with the workpiece.Hereinafter, an indexable cutting insert (see FIGS. 1 to 5) will bedescribed as a specific example.

FIG. 1 is a perspective view of the cutting tool in one embodiment byway of example. FIG. 2 is a cross section taken along a line X-Xindicated in FIG. 1. The cutting tool having such a shape is used as anindexable cutting insert for turning or the like.

Cutting tool 1 shown in FIGS. 1 and 2 has a surface including a topsurface, a bottom surface, and four side surfaces, and is generally inthe form of a quadrangular prism which is more or less smaller inthickness in the vertical direction. Further, cutting tool 1 has athroughhole penetrating it through the top and bottom surfaces, and thefour side surfaces at their boundary portions have adjacent ones thereofconnected by an arcuate surface.

Cutting tool 1 has the top and bottom surfaces to form a rake face 1 a,the four side surfaces (and each arcuate surface connecting adjacentones thereof together) to form flank face 1 b, and an arcuate surfaceconnecting rake face 1 a and flank face 1 b together to form a cuttingedge portion 1 c (see FIG. 2).

FIG. 3 is a partial enlarged view of FIG. 2. In FIG. 3, an imaginaryplane A, an imaginary boundary line AA, an imaginary plane B, and animaginary boundary line BB are shown.

Imaginary plane A corresponds to a plane obtained by extending rake face1 a. Boundary line AA is a boundary line between rake face 1 a andcutting edge surface 1 c. Imaginary plane B corresponds to a planeobtained by extending flank face 1 b. Boundary line BB is a boundaryline between flank face 1 b and cutting edge surface 1 c.

The example shown in FIG. 3 shows cutting edge portion 1 c having anarcuate surface (or honed), and rake face 1 a and flank face 1 bconnected via cutting edge portion 1 c.

Note that, in FIG. 3, imaginary planes A and B are each indicated by aline, and boundary lines AA and BB are each indicated by a dot.

While FIGS. 1-3 show cutting edge portion 1 c having an arcuate surface(or honed), the shape of cutting edge portion 1 c is not limitedthereto. For example, as shown in FIG. 4, cutting edge portion 1 c mayhave a planar shape (or a negative land). Further, as shown in FIG. 5,cutting edge portion 1 c may have a shape having a flat surface and anarcuate surface combined together (a shape having a honing and anegative land combined together).

As well as the example shown in FIG. 3, the examples shown in FIGS. 4and 5 also have rake face 1 a and flank face 1 b connected via cuttingedge portion 1 c, and imaginary plane A, boundary line AA, imaginaryplane B, and boundary line BB are set.

When cutting tool 1 is thus shaped as shown in FIGS. 3 to 5, cuttingedge portion 1 c can be determined from that shape alone. This isbecause cutting edge portion 1 c in that case is not included in eitherimaginary plane A or imaginary plane B and rake face 1 a and flank face1 b are visually distinguishable.

Cutting edge portion 1 c may generally be a surface of substrate 10 ofcutting tool 1, as will be described hereinafter, formed by machining aridge formed by planes. In other words, substrate 10 is obtained bymachining at least a portion of a surface of a precursor of thesubstrate composed of a sintered material or the like, and cutting edgeportion 1 c may include a surface formed through chamfering bymachining.

While the shape of cutting tool 1 and the name of each part thereof havebeen described with reference to FIGS. 1-5, substrate 10 of the cuttingtool according to the present embodiment, the shape of substrate 10according to the present embodiment and the name of each part thereofthat correspond to those of cutting tool 1 will be indicated by similarterminology. That is, substrate 10 of the cutting tool has rake face 1a, flank face 1 b, and cutting edge portion 1 c connecting rake face 1 aand flank face 1 b together.

<Substrate>

The substrate of the present embodiment can be any substrateconventionally known as a substrate of this type. For example, itpreferably includes at least one selected from the group consisting of acemented carbide (for example, a tungsten carbide (WC)-base cementedcarbide, a cemented carbide containing Co other than WC, a cementedcarbide with a carbonitride of Cr, Ti, Ta, Nb, or the like other than WCadded, or the like), a cermet (containing Tic, TiN, TiCN, or the like asa major component), a high-speed steel, ceramics (titanium carbide,silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, andthe like), a cubic boron nitride sintered material (a cBN sinteredmaterial), and a diamond sintered material.

Of these various types of substrates, it is particularly preferable toselect a cemented carbide (a WC-base cemented carbide, in particular) ora cermet (a TiCN-base cermet, in particular). This is because thesesubstrates are particularly excellent in balance between hardness andstrength at high temperature, in particular, and present excellentcharacteristics as a substrate for a cutting tool for theabove-described application.

When using a cemented carbide as a substrate, the effect of the presentembodiment is exhibited even if the cemented carbide has a structureincluding free carbon or an extraordinary phase referred to as η phase.Note that the substrate used in the present embodiment may have itssurface modified. For example, for the cemented carbide, the surface maybe provided with a β-free layer, and for the cermet, the surface may beprovided with a surface hardened layer, and even if the surface ismodified in this way, the effect of the present embodiment is exhibited.

<Coating>

A coating according to the present embodiment includes an AITiN layerprovided on the substrate. The “coating” coats at least a part of thesubstrate (for example, a rake face that comes into contact with chipsduring a cutting process, a flank face that comes into contact with aworkpiece, and the like) to exhibit a function to improve the cuttingtool's various characteristics such as breaking resistance, wearresistance (e.g., crater wear resistance, flank wear resistance and thelike), peeling resistance, and the like. The coating is preferablyapplied not only to a part of the substrate but also to the entiresurface of the substrate. However, even if the substrate is partiallyuncoated with the coating or the coating is partially different inconfiguration, such does not depart from the scope of the presentembodiment.

The coating's thickness is preferably 2.5 μm or more and 30 μm or less,more preferably 3 μm or more and 25 μm or less. Note that the coating'sthickness means a total in thickness of any layers constituting thecoating. A “layer constituting the coating” includes an AlTiN layer, anunderlying layer, a surface layer and the like, as will be describedhereinafter. For example, the thickness of the coating is measured bymeasuring any 10 points in a sample in a cross section parallel to thedirection of a normal to a surface of the substrate with a scanningtransmission electron microscope (STEM), and calculating an averagevalue of the measured 10 points in thickness. The same applies whenmeasuring in thickness the AITiN layer, the underlying layer, thesurface layer and the like described hereinafter. The scanningtransmission electron microscope is JEM-2100F (trade name) manufacturedby JEOL Ltd., for example.

(AlTiN Layer)

The AlTiN layer of the present embodiment contains cubic typeAl_(x)Ti_(1-x)N crystal grains (hereinafter also simply referred to as“crystal grains”). That is, the AlTiN layer is a layer includingpolycrystalline Al_(x)Ti_(1-x)N. In the present embodiment, “crystalgrains of Al_(x)Ti_(1-x)N” mean crystal grains each of a compositecrystal formed of a layer made of AlN (aluminum nitride) (hereinafteralso referred to as an “AlN layer”) and a layer made of TiN (titaniumnitride) (hereinafter also referred to as a “TiN layer”) alternatelystacked. In the present embodiment, the AlN layer also includes a layerhaving a portion with Al substituted with Ti. Further, the TiN layeralso includes a layer having a portion with Ti substituted with Al. Forcubic type Al_(x)Ti_(1-x)N crystal grains, the AlN layer and the TiNlayer both have an FCC structure (Face-Centered Cubic structure). Forhexagonal type Al_(x)Ti_(1-x)N crystal grains described hereinafter, theAlN layer and the TiN layer both have an HCP structure (HexagonalClose-Packed structure). An atomic ratio x of Al (aluminum) inAl_(x)Ti_(1-x)N is 0.7 or more and less than 0.95, preferably 0.8 ormore and 0.9 or less. The x can be determined by analyzing crystalgrains in the AlTiN layer appearing in the cross section of the sampledescribed above with an energy dispersive X-ray (EDX) spectrometeraccompanying a scanning electron microscope (SEM) or a TEM. The atomicratio x of Al thus determined is a value determined as an average of allof the crystal grains of Al_(x)Ti_(1-x)N. Specifically, each of any 10points in the AlTiN layer in the cross section of the sample is measuredto obtain a value of the x, and an average value of such values obtainedat the 10 points is defined as x in the Al_(x)Ti_(1-x)N. Herein, “any 10points” are selected from different crystal grains of the AlTiN layer.The EDX device is JED-2300 (trade name) manufactured by JEOL Ltd., forexample. Not only the atomic ratio of Al but those of Ti and N can alsobe calculated in the above method.

In the present embodiment, being “provided on the substrate” is notlimited to being provided directly on the substrate and also includesbeing provided on the substrate via another layer. That is, the AlTiNlayer may be provided directly on the substrate or may be provided onthe substrate via another layer such as an underlying layer describedhereinafter insofar as such does not impair an effect of the cuttingtool according to the present embodiment.

In one aspect of the present embodiment, being “provided on thesubstrate” can also be understood as being “disposed on the substrate.”That is, it can also be understood that the AlTiN layer may be disposeddirectly on the substrate or may be disposed on the substrate viaanother layer such as an underlying layer described hereinafter.

The AlTiN layer may be provided thereon with another layer such as asurface layer. The AlTiN layer may be an outermost surface of thecoating.

The AlTiN layer has the following feature: That is, the AlTiN layerincludes a central portion, and the central portion is a regionsandwiched between an imaginary plane D and an imaginary plane E, theimaginary plane D being an imaginary plane which passes through a point1 μm away in a direction of thickness from a first interface located onthe side of the substrate and is parallel to the first interface, theimaginary plane E being an imaginary plane which passes through a point1 μm away from a second interface opposite to the side of the substratein the direction of thickness and is parallel to the second interface.The first interface is parallel to the second interface. When a crosssection of the AlTiN layer obtained when cut along a plane including anormal to the second interface at the rake face and a normal to thesecond interface at the flank face is subjected to an electronbackscattering diffraction image analysis using a field emissionscanning microscope to determine a crystal orientation of each of theAl_(x)Ti_(1-x)N crystal grains and a color map is created based thereon,

then, in the color map,

the central portion at the rake face is occupied in area at a ratio of50% or more and less than 80% by Al_(x)Ti_(1-x)N crystal grains having a(111) plane with a normal thereto having a direction within ±15° withrespect to the direction of the normal to the second interface at therake face (hereinafter also referred to as “(111) oriented crystalgrains”), and

the central portion at the cutting edge portion is occupied in area at aratio of 80% or more by Al_(x)Ti_(1-x)N crystal grains having the (111)plane with a normal thereto having a direction within ±15° with respectto the direction of a normal to the cutting edge portion.

Furthermore, the direction of the normal to the cutting edge portion ofthe substrate is a direction of a normal to imaginary plane C includinga boundary line on the substrate between the rake face and the cuttingedge portion and a boundary line on the substrate between the flank faceand the cutting edge portion.

In one aspect of the present embodiment, the central portion at theflank face is preferably occupied in area at a ratio of 50% or more andless than 80% by Al_(x)Ti_(1-x)N crystal grains having the (111) planewith a normal thereto having a direction within ±15° with respect to thedirection of the normal to the second interface at the flank face.

Reference will now be made to FIG. 9 to specifically describe a methodfor creating the color map. First interface 11 a of AlTiN layer 11 shownin FIG. 9 is an interface located on the side of substrate 10, andsecond interface 11 b thereof is an interface located opposite to theside of substrate 10. First interface 11 a is parallel to secondinterface 11 b. When AlTiN layer 11 is the outermost surface of thecoating, second interface 11 b will be a surface of AlTiN layer 11.First interface 11 a is a straight line that passes a center between astraight line L1 that passes through a point on the side of thesubstrate farthest from the substrate in the direction of a normal to amajor surface of the substrate in the color map and is also parallel tothe major surface of the substrate and a straight line L2 that passesthrough a point on the side of the substrate closest to the substrate inthe same direction and is also parallel to the major surface of thesubstrate. Second interface 11 b is a straight line that passes a centerbetween a straight line M1 that passes through a point on the sideopposite to the substrate farthest from the substrate in the directionof the normal to the major surface of the substrate in the color map andis also parallel to the major surface of the substrate and a straightline M2 that passes through a point on the side opposite to thesubstrate closest to the substrate in the same direction and is alsoparallel to the major surface of the substrate. Note, however, that anapparently unexpected point is excluded in selecting the “point closestto the substrate” and the “point farthest from the substrate.”

Initially, the AlTiN layer is formed on the substrate based on a methoddescribed hereinafter. The formed AlTiN layer is cut so as to obtain across section perpendicular to the AlTiN layer including the substrateand the like. That is, the cutting is done so as to expose a cut surfaceof the AlTiN layer cut along a plane including a normal to the secondinterface at the rake face and a normal to the second interface at theflank face. After that, the cut surface is polished with waterproofabrasive paper (including SiC grain abrasive as an abrasive).

Note that the cutting is done for example as follows: wax or the like isused to closely fix AITiN layer 11 at a surface thereof (or a surface ofa coating when another layer is formed on AITiN layer 11) on asufficiently large holding flat plate and thereafter, a rotary bladecutter is used to cut the layer in a direction perpendicular to the flatplate (i.e., cut the layer such that the rotary blade is as vertical aspossible to the flat plate). While this cutting can be performed at anyportion of AlTiN layer 11 insofar as it is performed in such a verticaldirection, it is preferably done in a vicinity of cutting edge portion 1c, as will be described hereinafter.

Furthermore, the cut surface is polished with the waterproof abrasivepaper (with #400, followed by #800 followed by #1500). The numbers (#)of the waterproof abrasive paper mean differences in grain size of theabrasive, and a larger number indicates that the abrasive has a smallergrain size.

Subsequently, the polished surface is further smoothed by ion millingusing Ar ions. The ion milling was performed under the followingconditions:

-   Acceleration voltage: 6 kV-   Irradiation angle: 0° from the direction of a normal to second    interface 11 b of the AlTiN layer (that is, the direction of a    straight line parallel to the direction of the thickness of the    AlTiN layer at the cut surface)-   Irradiation time: 8 hours

Subsequently the smoothed cross-section (a mirror surface) is observedwith a field emission type scanning electron microscope (FE-SEM)(product name: “SU6600” manufactured by Hitachi High-Tech Corporation)equipped with an electron back-scattered diffractometer (an EBSD device)to obtain an image, which is subjected to an EBSD analysis. While wherethe smoothed cross section is observed is not particularly limited, itis preferable to observe it in a vicinity of cutting edge portion 1 c.The observation with the FE-SEM is conducted at a magnification of 5000times.

For the EBSD analysis, data is successively collected by positioning afocused electron beam on each pixel individually. In doing so, thefocused electron beam is set so that it is reflected at the AlN layer inthe crystal grain of Al_(x)Ti_(1-x)N. In the crystal grain, Al has ahigher atomic ratio than Ti, and accordingly, the number of AlN layersis larger than the number of TiN layers. Therefore, the presentinventors consider that the crystal orientation of all of the crystalgrains can be determined by analyzing the crystal orientation of the AlNlayer in the crystal grain. A normal to a sample surface (the smoothedcross section of the AlTiN layer) is inclined by 70 degrees with respectto the incident beam, and the analysis is conducted at 15 kV. In orderto avoid a charging effect, a pressure of 10 Pa is applied. A highcurrent mode is used in conformity with an aperture diameter of 60 μm or120 μm. Data is collected on the cross section for 100×500 pointscorresponding to a surface area (an observation area) of 10 μm (in thedirection of the thickness of the AlTiN layer)×50 μm (in a directionparallel to an interface of the AlTiN layer) in steps of 0.1 μm/step. Indoing so, measurement is done in three or more fields of view.

A result of the EBSD analysis is analyzed using commercially availablesoftware (trade name: “Orientation Imaging Microscopy Ver 6.2”,manufactured by EDAX Inc.) to create the color map. Specifically,initially, the crystal orientation of each crystal grain included in thecross section of AlTiN layer 11 is determined. The crystal orientationof each crystal grain determined herein is a crystal orientationobserved when each crystal grain appearing in the cross section of AlTiNlayer 11 is observed in a plan view in the direction of a normal to thatcross section (i.e., a direction penetrating the plane of the sheet ofFIG. 9). Then, based on the obtained crystal orientation of each crystalgrain, the crystal orientation of each crystal grain in the direction ofthe normal to a surface of AlTiN layer 11 (that is, second interface 11b) is determined. A color map is created based on the determined crystalorientation. The color map can be created using a method of “CrystalDirection MAP” included in the above software. Note that the color mapis created across an entire area of AlTiN layer 11 observed at the cutsurface in the direction of the thickness of the layer. In addition, acrystal grain which is partially outside a field of view for measurementis also counted as one crystal grain.

In FIG. 9, each area surrounded by a solid line and hatched is a (111)oriented crystal grains 11 d. Further, each area surrounded by a solidline and unhatched is a crystal grain which does not correspond to a(111) oriented crystal grain. That is, in FIG. 9, crystal grains 11 dhaving the (111) plane with a normal thereto having a direction within±15° with respect to the direction of a normal to second interface 11 bof AlTiN layer 11 is hatched. Although the color map is originallyrepresented in color, in the present specification it is schematicallyrepresented in monotone for the sake of convenience. Furthermore, inFIG. 9, there is an area shown in black, which is regarded as an area ofa crystal grain having its crystal orientation undetermined in the abovemethod.

In the present embodiment, an Al_(x)Ti_(1-x)N crystal grain's crystalorientation is determined in a central portion 11 c of AlTiN layer 11,as shown in FIG. 9. Central portion 11 c is a region sandwiched betweenan imaginary plane D and an imaginary plane E, the imaginary plane Dbeing an imaginary plane which passes through a point away in thedirection of thickness from first interface 11 a located on the side ofthe substrate and is parallel to first interface 11 a, the imaginaryplane E being an imaginary plane which passes through a point 1 μm awayfrom second interface 11 b opposite to the side of the substrate in thedirection of thickness and is parallel to second interface 11 b.Imaginary plane D and imaginary plane E can be set on the created colormap based on the distance from first interface 11 a or second interface11 b.

Note that when cutting edge portion 1 c is honed (for example, in thecase of FIG. 3), central portion 11 c of cutting edge portion 1 c is setin the following manner. Initially, the AlTiN layer is divided into aplurality of regions for each range in which curves representing firstand second interfaces 11 a and 11 b, respectively, in the color map canbe approximated to straight lines, respectively. Subsequently, centralportion 11 c is set according to the above method for each of thedivided regions. The set of central portions 11 c of the divided regionsthus set define central portion 11 c of cutting edge portion 1 c.Further, when cutting edge portion 1 c is honed or the like, a (111)oriented crystal grain in cutting edge portion 1 c means a crystal grainhaving a (111) plane with a normal thereto having a direction within±15° with respect to the direction of a normal to imaginary plane Cincluding a boundary line AA on the substrate between the rake face andthe cutting edge portion and a boundary line BB on the substrate betweenthe flank face and the cutting edge portion.

In the color map, the central portion at the rake face is occupied inarea at a ratio of 50% or more and less than 80%, preferably 60% or moreand 79% or less, more preferably 65% or more and 78% or less byAl_(x)Ti_(1-x)N crystal grains having a (111) plane with a normalthereto having a direction within ±15° with respect to the direction ofa normal to the second interface at the rake face. Herein, a ratio inarea is a ratio in area with reference to the entirety in area ofcentral portion 11 c in the color map.

In the color map, the central portion at the flank face is occupied inarea at a ratio preferably of 50% or more and less than 80%, morepreferably 60% or more and 79% or less, still more preferably 65% ormore and 79% or less by Al_(x)Ti_(1-x)N crystal grains having a (111)plane with a normal thereto having a direction within ±15° with respectto the direction of the normal to the second interface at the flankface. Herein, a ratio in area is a ratio in area with reference to theentirety in area of central portion 11 c in the color map.

In the color map, the central portion at the cutting edge portion isoccupied in area at a ratio of 80% or more, preferably 81% or more and98% or less, more preferably 81% or more and 95% or less byAl_(x)Ti_(1-x)N crystal grains having a (111) plane with a normalthereto having a direction within ±15° with respect to the direction ofa normal to the cutting edge portion. The direction of the normal tocutting edge portion 1 c is the direction of a normal to imaginary planeC including boundary line AA on substrate 10 between rake face 1 a andcutting edge portion 1 c and boundary line BB on substrate 10 betweenflank face 1 b and cutting edge portion 1 c (see FIGS. 3 to 5). Herein,a ratio in area is a ratio in area with reference to the entirety inarea of central portion 11 c in the color map.

In the cutting tool according to the present embodiment, the cuttingedge portion at the central portion of the AITiN layer is occupied inarea by (111) oriented crystal grains at a ratio of 80% or more. The(111) oriented crystal grain has a close-packed structure and has highhardness. Therefore, the cutting tool has excellent flank wearresistance. The cutting tool can be suitably used for processing a highhardness material (for example, SKD material) in particular.

The AITiN layer includes cubic Al_(x)Ti_(1-x)N crystal grains. In oneaspect of the present embodiment, the AlTiN layer may further includehexagonal Al_(x)Ti_(1-x)N crystal grains unless such impairs an effectof the present disclosure. The cubic AI_(x)Ti_(1-x)N crystal grain andthe hexagonal Al_(x)Ti_(1-x)N crystal grain are distinguished by, forexample, a pattern of a diffraction peak obtained through x-raydiffraction.

When a total amount of crystal grains of cubic Al_(x)Ti_(1-x)N (c) andcrystal grains of hexagonal Al_(x)Ti_(1-x)N (h) serves as a reference,the crystal grains of hexagonal Al_(x)Ti_(1-x)N are contained at aproportion (h/(c+h)) preferably of 0 to 15% by volume, more preferably 0to 10% by volume. The proportion can be determined for example byanalyzing a pattern of a diffraction peak obtained through x-raydiffraction. A specific method is employed, as follows:

An X-ray spectrum of the AlTiN layer at the cross section of the sampleas set forth above is obtained using an X-ray diffractometer(“MiniFlex600” (trade name) manufactured by Rigaku Corporation). TheX-ray diffractometer's conditions are for example as follows:

-   Characteristic X-ray: Cu-Kα (wavelength: 1.54 angstrom)-   Tube voltage: 45 kV-   Tube current: 40 mA-   Filter: Multi-layer mirror-   Optical system: Focusing method-   X-ray diffraction method: θ-2θ method

In the obtained X-ray spectrum, cubic Al_(x)Ti_(1-x)N's peak intensity(Ic) and hexagonal Al_(x)Ti_(1-x)N's peak intensity (Ih) are measured.Herein, a “peak intensity” means a peak's height (cps) in the X-rayspectrum. Cubic Al_(x)Ti_(1-x)N's peak can be confirmed arounddiffraction angles 2θ=38° and 44°. Hexagonal Al_(x)Ti_(1-x)N's peak canbe confirmed around a diffraction angle 2θ=33°. A peak intensity is avalue excluding a background.

When a total amount of the cubic Al_(x)Ti_(1-x)N and the hexagonalAl_(x)Ti_(1-x)N serves as a reference, the hexagonal Al_(x)Ti_(1-x)N iscontained at a proportion (vol %), as calculated by an expressionindicated hereinafter. The cubic Al_(x)Ti_(1-x)N's peak intensity (Ic)is obtained by the sum of a peak intensity around θ=38° and a peakintensity around θ=44°.

Proportion of the hexagonal Al_(x)Ti_(1-x)N contained (vol%)=Ih/(Ih+Ic)×100

(Thickness of AlTiN Layer)

In the present embodiment, the AlTiN layer has a thickness preferably of2.5 μm or more and 20 μm or less, more preferably 3 μm or more and 20 μmor less, still more preferably 5 μm or more and 15 μm or less. Thisallows such an excellent effect as above to be presented.

When the AlTiN layer has a thickness of less than 2.5 μm, wearresistance attributed to the presence of the AlTiN layer (crater wearresistance and flank wear resistance) tends to be less improved. Whenthe AlTiN layer has a thickness exceeding 20 μm, an interfacial stressattributed to a difference in linear expansivity between the AlTiN layerand another layer is increased, and crystal grains of Al_(x)Ti_(1-x)Nmay escape from the AlTiN layer.

(Underlying Layer)

The coating preferably further includes an underlying layer providedbetween the substrate and the AlTiN layer, and the underlying layer iscomposed preferably of a compound consisting of at least one elementselected from the group consisting of a group 4 element, a group 5element and a group 6 element of the periodic table and aluminum (Al)and at least one element selected from the group consisting of carbon,nitrogen, oxygen and boron. Examples of the Group 4 element of theperiodic table include titanium (Ti), zirconium (Zr), hafnium (Hf), andthe like. Examples of the Group 5 element of the periodic table includevanadium (V), niobium (Nb), tantalum (Ta), and the like. Examples of theGroup 6 element of the periodic table include chromium (Cr), molybdenum(Mo), tungsten (W), and the like. The underlying layer is preferablycomposed of a compound represented by TiCN. Such an underlying layerexhibits strong adhesion to the AlTiN layer. As a result, the coating isenhanced in peel resistance.

The underlying layer preferably has a thickness of 0.1 μm or more and 20μm or less, more preferably 1 μm or more and 15 μm or less. Such athickness can be confirmed by observing a vertical cross section of thesubstrate and the coating with a scanning transmission electronmicroscope (STEM) or the like, similarly as has been described above.

(Surface Layer)

The coating preferably further includes a surface layer provided on theAlTiN layer, and

the surface layer is composed preferably of a compound consisting of atleast one element selected from the group consisting of a group 4element, a group 5 element and a group 6 element of the periodic tableand aluminum (Al) and at least one element selected from the groupconsisting of carbon, nitrogen, oxygen and boron.

The compound included in the surface layer includes Al₂O₃ and TiN forexample.

The surface layer preferably has a thickness of 0.1 μm or more and 3 μmor less, more preferably 0.3 μm or more and 2 μm or less. Such athickness can be confirmed by observing a vertical cross section of thesubstrate and the coating with a scanning transmission electronmicroscope (STEM) or the like, similarly as has been described above.

(Another Layer)

The coating may further include another layer insofar as it does notimpair an effect of the cutting tool according to the presentembodiment. The other layer may have a composition different from oridentical to that of the AlTiN layer, the underlying layer, or thesurface layer. Examples of the compound included in the other layerinclude TiN, TiCN, TiBN, and Al₂O₃. The other layer is not limited,either, in in what order it is stacked. For example, an example of theother layer is an intermediate layer provided between the underlyinglayer and the AlTiN layer. While the other layer is not particularlylimited in thickness as long as it does not impair an effect of thepresent embodiment, it is for example 0.1 μm or more and 20 μm or less.

<<Method for Manufacturing a Surface-Coated Cutting Tool>>

A method for manufacturing a cutting tool according to the presentembodiment includes:

a first step of preparing the substrate (hereinafter also simplyreferred to as a “first step”);

a second step of depositing the AlTiN layer on the substrate throughchemical vapor deposition (hereinafter also simply referred to as a“second step”); and

a third step of blasting the AlTiN layer (hereinafter also simplyreferred to as a “third step”),

the second step including jetting a first gas, a second gas and a thirdgas onto the substrate in an atmosphere of 650° C. or higher and 900° C.or lower and 0.5 kPa or higher and 30 kPa or lower, the first gasincluding a gas of a halide of aluminum and a gas of a halide oftitanium, the second gas including a gas of a halide of aluminum, a gasof a halide of titanium and a gas of ammonia, the third gas including agas of ammonia.

<First Step: Step of Preparing a Substrate>

In the first step, a substrate is prepared. For example, a cementedcarbide substrate is prepared as the substrate. The cemented carbidesubstrate may be a commercially available product or may be manufacturedin a typical powder metallurgy method. When manufactured in a typicalpowder metallurgy method, for example, WC powder and Co powder are mixedusing a ball mill or the like to obtain a powdery mixture. After thepowdery mixture is dried, it is shaped into a prescribed shape (forexample, SEET13T3AGSN-G, etc.) to obtain a shaped body. The shaped bodyis sintered to obtain a WC-Co based cemented carbide (a sinteredmaterial). Subsequently, the sintered material can be honed or subjectedto a prescribed cutting edge process to prepare a substrate made of theWC-Co based cemented carbide. In the first step, any other substrate maybe prepared insofar as it is a substrate conventionally known as asubstrate of this type.

<Second Step: Step of Jetting First Gas, Second Gas and Third Gas to theSubstrate to Form an AlTiN Layer>

In the second step, a first gas, a second gas and a third gas are jettedonto the substrate in an atmosphere of 650° C. or higher and 900° C. orlower and 0.5 kPa or higher and 30 kPa or lower, the first gas includinga gas of a halide of aluminum and a gas of a halide of titanium, thesecond gas including a gas of a halide of aluminum, a gas of a halide oftitanium and a gas of ammonia, the third gas including a gas of ammonia.This step can be performed using, for example, a CVD apparatus describedbelow.

(CVD Apparatus)

FIG. 10 is a schematic cross section of one example of a CVD apparatusused for manufacturing the cutting tool according to the presentembodiment. As shown in FIG. 10, a CVD apparatus 50 includes a pluralityof substrate setting jigs 52 for setting substrate 10, and a reactionchamber 53 made of heat-resistant alloy steel and including substratesetting jigs 52 therein. A temperature controller 54 is provided aroundreaction chamber 53 for controlling the temperature inside reactionchamber 53. In the present embodiment, substrate 10 is set on aprotrusion provided on substrate setting jig 52.

A gas introduction pipe 58 having a first gas introduction pipe 55, asecond gas introduction pipe 56 and a third gas introduction pipe 57adjacently bonded together extends in the vertical direction through aspace inside reaction chamber 53 rotatably about the vertical direction.Gas introduction pipe 58 is configured such that the first gasintroduced into first gas introduction pipe 55, the second gasintroduced into second gas introduction pipe 56, and the third gasintroduced into third gas introduction pipe 57 are not mixed togetherinside gas introduction pipe 58 (see FIG. 11). Further, first gasintroduction pipe 55, second gas introduction pipe 56, and third gasintroduction pipe 57 are each provided with a plurality of throughholesfor jetting the gases respectively flowing through first, second andthird gas introduction pipes 55, 56 and 57 onto substrate 10 set onsubstrate setting jig 52. In the present embodiment, the gas jettingthroughholes are preferably positioned at the central portion of flankface 10 b of substrate 10. It is preferable that the gas jettingthroughhole and substrate 10 be spaced by a short distance. Thus settingthe throughholes allows deposition to be done to allow the cutting edgeportion to have many (111) oriented crystal grains.

Further, reaction chamber 53 is provided with a gas exhaust pipe 59 forexternally exhausting the gas inside reaction chamber 53, and the gas inreaction chamber 53 passes through gas exhaust pipe 59 and is exhaustedout of reaction chamber 53 via a gas exhaust port 60.

More specifically, the first gas, the second gas and the third gas areintroduced into first gas introduction pipe 55, second gas introductionpipe 56 and third gas introduction pipe 57, respectively. In doing so,the first, second and third gases in their respective gas introductionpipes may have any temperature that does not liquefy the gases.Subsequently, the first gas, the second gas and the third gas are jettedin this order repeatedly into reaction chamber 53 with an atmosphere settherein to have a temperature of 650° C. or higher and 900° C. or lower(preferably 700° C. or higher and 770° C. or lower) and a pressure of0.5 kPa or higher and 30 kPa or lower (preferably 2 kPa or higher and 5kPa or lower). As gas introduction pipe 58 has the plurality ofthroughholes, the first, second, and third gases introduced are jettedinto reaction chamber 53 through different throughholes, respectively.While the gases are thus jetted, gas introduction pipe 58 is rotating ata rotation speed for example of 2 to 4 rpm about the above-mentionedaxis, as indicated in FIG. 10 by a rotating arrow. As a result, thefirst gas, the second gas, and the third gas can be jetted in this orderrepeatedly onto substrate 10.

(First Gas)

The first gas includes a gas of a halide of aluminum and a gas of ahalide of titanium.

An example of the gas of a halide of aluminum is for example a gas ofaluminum chloride (a gas of AlCl₃ and a gas of Al₂Cl₆). Preferably, agas of AlCl₃ is used. The gas of a halide of aluminum preferably has aconcentration (% by volume) of 0.3% by volume or more and 1.5% by volumeor less, more preferably 0.8% by volume or more and 0.87% by volume orless with reference to the total volume of the first gas.

Examples of the gas of a halide of titanium include a gas of titanium(IV) chloride (a gas of TiCl₄), a gas of titanium (III) chloride (a gasof TiCl₃). Preferably a gas of titanium (IV) chloride is used. The gasof a halide of titanium preferably has a concentration (in % by volume)of 0.1% by volume or more and 1% by volume or less, more preferably 0.1%by volume or more and 0.2% by volume or less with reference to the totalvolume of the first gas.

In the first gas, the gas of a halide of aluminum has a molar ratiopreferably of 0.5 or more and 0.9 or less, more preferably 0.8 or moreand 0.87 or less with reference to the total moles of the gas of ahalide of aluminum and the gas of a halide of titanium.

The first gas may include a gas of hydrogen and may include an inert gassuch as a gas of argon. The inert gas preferably has a concentration (%by volume) of 5% by volume or more and 70% by volume or less, morepreferably 20% by volume or more and 60% by volume or less withreference to the total volume of the first gas. The gas of hydrogentypically occupies the balance of the first gas.

The first gas is jetted onto the substrate at a flow rate preferably of20 to 40 L/min.

(Second Gas)

The second gas includes a gas of a halide of aluminum, a gas of a halideof titanium, and a gas of ammonia. The gas of a halide of aluminum andthe gas of a halide of titanium can be the gases exemplified in theabove (First Gas) section. The gas of a halide of aluminum and the gasof a halide of titanium that are used for the first gas may be identicalto or different from the gas of a halide of aluminum and the gas of ahalide of titanium that are used for the second gas, respectively.

The gas of a halide of aluminum preferably has a concentration (% byvolume) of 4% by volume or more and 5% by volume or less, morepreferably 4.3% by volume or more and 4.5% by volume or less withreference to the total volume of the second gas.

The gas of a halide of titanium preferably has a concentration (in % byvolume) of 0.1% by volume or more and 1% by volume or less, morepreferably 0.5% by volume or more and 0.8% by volume or less withreference to the total volume of the second gas.

In the second gas, the gas of a halide of aluminum has a molar ratiopreferably of 0.82 or more and 0.95 or less, more preferably 0.85 ormore and 0.9 or less with reference to the total moles of the gas of ahalide of aluminum and the gas of a halide of titanium.

The gas of ammonia preferably has a concentration (% by volume) of 5% byvolume or more and 15% by volume or less, more preferably 8% by volumeor more and 10% by volume or less with reference to the total volume ofthe second gas.

The second gas may include a gas of hydrogen and may include an inertgas such as a gas of argon. The inert gas preferably has a concentration(% by volume) of 5% by volume or more and 50% by volume or less, morepreferably 15% by volume or more and 17% by volume or less withreference to the total volume of the second gas. The gas of hydrogentypically occupies the balance of the second gas.

The second gas is jetted onto the substrate at a flow rate preferably of20 to 40 L/min.

(Third Gas)

The third gas includes a gas of ammonia. The third gas may include a gasof hydrogen and may include an inert gas such as a gas of argon.

The gas of ammonia preferably has a concentration (% by volume) of 2% byvolume or more and 30% by volume or less, more preferably 2% by volumeor more and 10% by volume or less with reference to the total volume ofthe third gas. The gas of hydrogen typically occupies the balance of thethird gas.

The third gas is jetted onto the substrate at a flow rate preferably of10 to 20 L/min.

<Third Step: a Blasting Step>

In this step, the coating is subjected to blasting. The blasting isperformed for example under the conditions indicated below. The blastingcan impart compressive residual stress to the coating.

Blasting Conditions

Medium: 500 g of zirconia particles

-   Projection angle: 45°-   Projection distance: 50 mm-   Projection time: 3 seconds

<Another Step>

In the manufacturing method according to the present embodiment, inaddition to the steps described above, an additional step may beperformed, as appropriate, within a range that does not impair an effectof the present embodiment. Examples of the additional step include thestep of forming an underlying layer between the substrate and the AlTiNlayer, and the step of forming a surface layer on the AlTiN layer. Theunderlying layer and the surface layer may be formed in any method, andthe layers are formed for example through CVD. When the step of formingthe surface layer on the AlTiN layer is performed, the third step isperformed after the surface layer is formed.

In the method for manufacturing a cutting tool according to the presentembodiment, the AlTiN layer is formed through CVD. When this is comparedwith forming the coating through PVD, the former enhances the coating'sadhesion to the substrate (or coating adhesion).

What has been described above includes features given in the followingNotes.

(Note 1)

A surface-coated cutting tool including a rake face, a flank face, and acutting edge portion connecting the rake face and the flank facetogether,

the cutting tool comprising a substrate and an AlTiN layer provided onthe substrate,

the AlTiN layer including cubic Al_(x)Ti_(1-x)N crystal grains,

-   -   the atomic ratio x of Al in the Al_(x)Ti_(1-x)N being 0.7 or        more and less than 0.95,

the AlTiN layer including a central portion,

the central portion being a region sandwiched between an imaginary planeD and an imaginary plane E, the imaginary plane D being an imaginaryplane which passes through a point 1 μm away in a direction of thicknessfrom a first interface located on a side of the substrate and isparallel to the first interface, the imaginary plane E being animaginary plane which passes through a point 1 μm away from a secondinterface opposite to the side of the substrate in the direction ofthickness and is parallel to the second interface,

the first interface being parallel to the second interface,

when a cross section of the AlTiN layer obtained when cut along a planeincluding a normal to the second interface at the rake face and a normalto the second interface at the flank face is subjected to an electronbackscattering diffraction image analysis using a field emissionscanning microscope to determine a crystal orientation of each of theAl_(x)Ti_(1-x)N crystal grains and a color map is created based thereon,

in the color map,

the central portion at the rake face being occupied in area at a ratioof 50% or more and less than 80% by Al_(x)Ti_(1-x)N crystal grainshaving a (111) plane with a normal thereto having a direction within±15° with respect to the direction of the normal to the second interfaceat the rake face,

the central portion at the cutting edge portion being occupied in areaat a ratio of 80% or more by Al_(x)Ti_(1-x)N crystal grains having the(111) plane with a normal thereto having a direction within ±15° withrespect to a direction of a normal to the cutting edge portion,

the direction of the normal to the cutting edge portion being adirection of a normal to an imaginary plane C including a boundary lineon the substrate between the rake face and the cutting edge portion anda boundary line on the substrate between the flank face and the cuttingedge portion.

(Note 2)

The surface-coated cutting tool according to Note 1, wherein the AlTiNlayer has a thickness of 2.5 μm or more and 20 μm or less.

(Note 3)

The surface-coated cutting tool according to Note 1 or 2, furthercomprising an underlying layer provided between the substrate and theAlTiN layer, wherein the underlying layer is composed of a compoundconsisting of: at least one element selected from the group consistingof a group 4 element, a group 5 element and a group 6 element of theperiodic table and Al; and at least one element selected from the groupconsisting of carbon, nitrogen, oxygen and boron.

(Note 4)

The surface-coated cutting tool according to any one of Notes 1 to 3,further comprising a surface layer provided on the AlTiN layer, whereinthe surface layer is composed of a compound consisting of: at least oneelement selected from the group consisting of a group 4 element, a group5 element and a group 6 element of the periodic table and Al; and atleast one element selected from the group consisting of carbon,nitrogen, oxygen and boron.

EXAMPLES

Hereinafter, the present invention will more specifically be describedwith reference to examples although the present invention is not limitedthereto.

<<Manufacturing a Cutting Tool>>

<Preparing a Substrate>

Initially, as a substrate on which a coating to be formed, a substratecomposed of cemented carbide indicated in Table 1 below (hereinafteralso simply referred to as a “substrate”) was prepared (a first step).Specifically, initially, powdery raw materials of a blending composition(% by mass) shown in Table 1 were uniformly mixed. “Balance” in Table 1indicates that WC occupies the balance of the blending composition (% bymass).

TABLE 1 blending composition (mass %) type Co TiC Cr₃C₂ TaC WC substrate10.0 3 0.3 0.5 balance

Subsequently, the powdery mixture is pressure-formed into a prescribedshape and thereafter sintered for 1 to 2 hours at 1300 to1500° C. toobtain the above substrate (substrate shape (JIS standard):SEET13T3AGSN-G, cutter diameter: 100). SEET13T3AGSN-G is a shape of anindexable cutting insert for a rotating tool.

<Preparing a Coating>

A coating was formed on a surface of the substrate by forming theunderlying layer, the AlTiN layer and the surface layer shown in Table 8on the surface of the substrate. The coating was formed mainly throughCVD. Hereinafter, a method for depositing each layer constituting thecoating will be described.

(Depositing an AlTiN Layer)

Under the conditions shown in Table 2 for deposition, a first gas, asecond gas, and a third gas having the compositions shown in Tables 3, 4and 5, respectively, were jetted in this order repeatedly onto a surfaceof the substrate to deposit an AlTiN layer (a second step). In doing so,the substrate was set on a protrusion provided on a substrate settingjig. Further, a spacing between the gas jetting throughholes and thesubstrate was set to be small (e.g., within 15 mm). The throughholeswere positioned at the central portion of the flank face of thesubstrate. When an underlying layer was provided on a surface of thesubstrate, an AlTiN layer was formed on a surface of the underlyinglayer.

For example, an AlTiN layer indicated in Table 6 by an identificationsymbol [1] was deposited as follows: with a temperature of 780° C., apressure of 3 kPa, and the gas introduction pipe having a rotationalspeed of 2 rpm set as conditions for deposition (as indicated in Table 2by an identification symbol 2-a), a first gas indicated in Table 3 by anidentification symbol 3-a (0.81% by volume of AlCl₃, 0.19% by volume ofTiCl₄, 60% by volume of Ar, and a balance of H₂, with a gas flow rate of20 L/min), a second gas indicated in Table 4 by an identification symbol4-a (4.3% by volume of AlCl₃, 0.8% by volume of TiCl₄, 8% by volume ofNH₃, 15% by volume of Ar, and a balance of H₂, with a gas flow rate of40 L/min), and a third gas indicated in Table 5 by an identificationsymbol 5-a (2% by volume of NH₃, and a balance is H₂, with a gas flowrate of 10 L/min) were jetted in this order repeatedly onto a surface ofthe substrate to deposit the AlTiN Layer. An AlTiN layer indicated inTable 6 by an identification symbol [8] was deposited in a known PVDmethod. Table 6 shows each deposited AlTiN layer's composition andothers.

TABLE 2 conditions for deposition identification symbol 2-a temperature(° C.) 780 pressure (kPa) 3 rotational speed (rpm) 2

TABLE 3 composition of 1st gas identification symbol 3-a 3-b 3-c 3-dAlCl₃ (vol %) 0.81 0.85 0.83 0.93 TiCl₄ (vol %) 0.19 0.15 0.17 0.07AlCl₃/(AlCl₃ + TiCl₄) 0.81 0.85 0.83 0.93 (molar ratio) Ar (vol %) 60 2060 20 H₂ (vol %) balance balance balance balance gas flow rate (L/min)20 20 20 20

TABLE 4 composition of 2nd gas identification symbol 4-a 4-b 4-c AlCl₃(vol %) 4.3 4.5 5.0 TiCl₄ (vol %) 0.8 0.5 0.5 AlCl₃/(AlCl₃ + TiCl₄) 0.850.90 0.91 (molar ratio) NH₃ (vol %) 8 10 14 Ar (vol %) 15 17 15 H₂ (vol%) balance balance balance gas flow rate (L/min) 40 40 40

TABLE 5 composition of 3rd gas identification symbol 5-a NH₃ (vol %) 2H₂ (vol %) balance gas flow rate (L/min) 10

TABLE 6 ratio in area of AlTiN layer (111) oriented atomic crystalgrains (%) identifi- h/(c + h) ratio x of cutting cation table tableratio Al in rake edge flank symbol 3 4 (vol %) Al_(x)Ti_(1−x)N faceportion face [1] 3-a 4-a 4 0.84 75 91 78 [2] 3-b 4-a 5 0.87 74 90 76 [3]3-c 4-a 4 0.85 78 93 79 [4] 3-a 4-b 4 0.86 71 88 75 [5] 3-c 4-b 5 0.8869 82 77 [6] 3-b 4-c 5 0.90 74 74 73 [7] 3-d 4-a 17 0.95 77 84 73 [8]*none none 3 0.65 82 83 82 *deposited in a known PVD method.

(Depositing an Underlying Layer and Depositing a Surface Layer)

Under conditions indicated in Table 7 for deposition, a reactant gashaving a composition indicated in Table 7 was jetted onto a surface ofthe substrate to deposit an underlying layer. Under conditions indicatedin Table 7 for deposition, a reactant gas having a composition indicatedin Table 7 was jetted onto a surface of the AlTiN layer to deposit asurface layer.

TABLE 7 conditions for deposition gas composition of pressuretemperature flow rate type reactant gas (vol %) (kPa) (° C.) (L/min) TiNTiCl₄ = 0.5%, N₂ = 41.2%, 79.8 780 45.9 H₂ = balance TiCN TiCl₄ = 2.0%,CH₃CN = 0.7%, 9 860 50.5 H₂ = balance Al₂O₃ AlCl₃ = 1.6%, CO₂ = 4.5%,6.7 850 46.2 H₂S = 0.2%, NO₂ = 0.5%, H₂ = balance

(Blasting)

The coating on the surface of the substrate was blasted under thefollowing conditions (a third step):

Blasting Conditions

-   Medium: 500 g of zirconia particles-   Projection angle: 45°-   Projection distance: 50 mm-   Projection time: 3 seconds

A cutting tool according to the present example was thus manufacturedthrough the above process. The cutting tools of Sample Nos. 1 and 4 to10 include a substrate, an AlTiN layer provided on the substrate, and anunderlying layer provided between the substrate and the AlTiN layer. Thecutting tools of Sample Nos. 2 and 3 include a substrate, an AlTiN layerprovided on the substrate, an underlying layer provided between thesubstrate and the AlTiN layer, and a surface layer provided on the AlTiNlayer.

<<Evaluating Characteristics of Cutting Tools>>

Using the cutting tools of the samples manufactured as described above,the cutting tools' characteristics were evaluated as follows: Thecutting tools of Sample Nos. 1 to 7 correspond to examples. The cuttingtools of Sample Nos. 8 to 10 correspond to comparative examples.

<Measuring Thickness of Coating and the Like>

The coating and the underlying, AlTiN and surface layers constitutingthe coating were measured in thickness by measuring each layer at any 10points of a sample in a cross section parallel to the direction of anormal to a surface of the substrate with a scanning transmissionelectron microscope (STEM) (manufactured by JEOL Ltd., trade name:JEM-2100F), and calculating an average value in thickness of themeasured 10 points. A result is shown in Table 8. In the “surface layer”column, “none” indicates that the surface layer does not exist in thecoating. Furthermore, in the “AlTiN layer” column, an indication such as“[1] (5.0)” indicates that an AlTiN layer has a configuration indicatedin Table 6 by identification symbol [1] and has a thickness of 5.0 μm.In Table 8, an indication such as “TiCN (1.0)” indicates that thecorresponding layer is a TiCN layer having a thickness of 1.0 μm. Twocompounds indicated in one column (for example, “Al₂O₃ (0.2)-TiN (0.1)”)indicate that the compound on the left side (Al₂O₃ (0.2)) is a layerlocated on a side closer to a surface of the substrate and the compoundon the right side (TiN (0.1)) is a layer located on a side farther fromthe surface of the substrate. Furthermore, an indication such as “[Al₂O₃(0.2)-TiN (0.1)]×3” or the like means that a layer represented by “Al₂O₃(0.2)-TiN (0.1)” is deposited three times repeatedly.

TABLE 8 coating's configuration & each layer's thickness underlyingAlTiN sample layer layer total coating nos. (μm) (μm) surface layer (μm)thickness (μm) 1 TiCN (1.0) [1] (5.0) none 6.0 2 TiCN (1.0) [1] (4.5)Al₂O₃ (0.5) 6.0 3 TiCN (0.5) [1] (3.6) [Al₂O₃(0.2)-TiN(0.1)] × 3 6.0 4TiCN (1.0) [2] (5.0) none 6.0 5 TiCN (1.0) [3] (5.0) none 6.0 6 TiCN(1.0) [4] (5.0) none 6.0 7 TiCN (1.0) [5] (5.0) none 6.0 8 TiCN (1.0)[6] (5.0) none 6.0 9 TiCN (1.0) [7] (5.0) none 6.0 10 none [8] (5.0)none 5.0

<Creating a Color Map>

Initially, the cutting tool was cut so that a cross sectionperpendicular to a surface (or an interface) of the AlTiN layer in thecoating was obtained. Subsequently, the cut surface was polished withwaterproof abrasive paper (manufactured by Noritake Coated Abrasive Co.,Ltd. (NCA), trade name: WATERPROOF PAPER, #400, #800, #1500) to preparea processed surface of the AlTiN layer. Subsequently, the processedsurface is further smoothed by ion milling using Ar ions. The ionmilling was performed under the following conditions:

-   Acceleration voltage: 6 kV-   Irradiation angle: 0° from the direction of a normal to the second    interface of the AlTiN layer (that is, the direction of a straight    line parallel to the direction of the thickness of the AlTiN layer    at the cut surface)-   Irradiation time: 6 hours

The thus prepared processed surface was observed with an EBSD equippedFE-SEM (trade name: “SU6600” manufactured by Hitachi High-TechnologiesCorporation) at a magnification of 5000 times to create a color map ofthe processed surface for an observation area of 10 μm (in the directionof the thickness of the AlTiN layer)×50 μm (in a direction parallel toan interface of the AlTiN layer). In doing so, an analysis was doneusing a focused electron beam set so that it was reflected at the AlNlayer in the crystal grains of Al_(x)Ti_(1-x)N. Three such color mapswere created (in other words, measurement was done in three fields ofview). Specifically, initially, the crystal orientation of each crystalgrain included in the cross section of the AlTiN layer was determined.The crystal orientation of each crystal grain as determined herein is acrystal orientation observed when each crystal grain appearing in thecross section of the AlTiN layer is viewed in a plan view in thedirection of a normal to that cross section (that is, a directionpenetrating the plane of the sheet of FIG. 9). Based on the crystalorientation of each crystal grain determined, the crystal orientation ofeach crystal grain in the direction of the normal to the secondinterface of the AlTiN layer was determined. A color map was createdbased on the determined crystal orientation (for example, see FIG. 9).For each color map, a ratio in area of the central portion of the AlTiNlayer occupied by (111) oriented crystal grains was determined usingcommercially available software (trade name: “Orientation ImagingMicroscopy Ver 6.2” manufactured by EDAX Inc.). A result thereof isshown in table 6. Note that the central portion is a region sandwichedbetween an imaginary plane D and an imaginary plane E, the imaginaryplane D being an imaginary plane which passes through a point 1 μm awayin a direction of thickness from a first interface located on the sideof the substrate and is parallel to the first interface, the imaginaryplane E being an imaginary plane which passes through a point 1 μm awayfrom a second interface opposite to the side of the substrate in thedirection of thickness and is parallel to the second interface. (Forexample, see FIG. 9).

Herein, the first interface and the second interface were defined in thecolor map, as follows: Initially, in the color map, the area of theAlTiN layer and that other than the AlTiN layer were differently coloredand displayed so that they were distinguishable. A straight line thatpasses a center between a straight line L1 that passes through a pointon the side of the substrate farthest from the substrate in thedirection of a normal to a major surface of the substrate in the colormap and is also parallel to the major surface of the substrate and astraight line L2 that passes through a point on the side of thesubstrate closest to the substrate in the same direction and is alsoparallel to the major surface of the substrate is defined as firstinterface 11 a (see FIG. 9 for example). A straight line that passes acenter between a straight line M1 that passes through a point on theside opposite to the substrate farthest from the substrate in thedirection of the normal to the major surface of the substrate in thecolor map and is also parallel to the major surface of the substrate anda straight line M2 that passes through a point on the side opposite tothe substrate closest to the substrate in the same direction and is alsoparallel to the major surface of the substrate is defined as the secondinterface (see FIG. 9 for example).

Table 6 shows a ratio in area of (111) oriented crystal grains at eachof the rake face, the cutting edge and the flank face. In the cuttingedge portion, crystal grains having the (111) plane with a normalthereto having a direction within ±15° with respect to the direction ofa normal to imaginary plane C including boundary line AA on thesubstrate between the rake face and the cutting edge portion andboundary line BB on the substrate between the flank face and the cuttingedge portion were considered as (111) oriented crystal grains.

<<Cutting Test>>

(Cutting Evaluation: Continuous Processing Test)

Using the cutting tools of the thus prepared samples (sample nos. 1 to10) under the cutting conditions indicated below, a cutting distance (m)reached when the flank face was worn by an amount of 0.25 mm or thecutting edge portion was broken was measured. Moreover, how the cuttingtools were damaged after cutting (or a final damaged state) wasobserved. A result thereof is shown in table 9. A cutting tool providinga longer cutting distance can be evaluated as a cutting tool havingbetter flank wear resistance. A cutting tool with no breakage observedin a damaged state after cutting can be evaluated as a cutting toolhaving excellent breaking resistance.

Test Conditions for Continuous Processing

-   Workpiece: SKD11 (a block material, W300×L50)-   Cutting speed: 200 m/min-   Feed rate: 0.12 mm/t-   Cutting Depth: 2 mm-   Cutting width: 60 mm-   Cutting oil: Dry type

TABLE 9 sample cutting nos. distance (m) final damaged state 1 3.3normally worn 2 3.3 normally worn 3 3.9 normally worn 4 3.0 normallyworn 5 3.6 normally worn 6 3.0 normally worn 7 3.0 normally worn 8 1.5abnormally worn, broken 9 0.9 broken 10 0.6 abnormally worn, broken

As can be seen in Table 9, the cutting tools of sample Nos. 1-7 (thatis, the cutting tools of the examples) provided a good result of acutting distance of 3.0 m or more in continuous processing. The cuttingtools of Sample Nos. 1 to 7 had their cutting edge portions unbroken andnormally worn (normally worn). In contrast, the cutting tools of samplenos. 8 to 10 (the cutting tools of the comparative examples) provided acutting distance of 1.5 m or less in continuous processing. The cuttingtools of Sample Nos. 8 and 10 had their flank faces abnormallysignificantly worn (abnormally worn). The cutting tools of Sample Nos.8, 9 and 10 were confirmed to have their cutting edge portions broken.From the above results, it has been found that the cutting tools of theexamples had excellent flank wear resistance. It has also been foundthat the cutting tools of the examples also have excellent breakingresistance.

Thus while embodiments and examples of the present invention have beendescribed, it is also initially planned to combine configurations of theembodiments and examples, as appropriate.

It should be understood that the embodiments and examples disclosedherein have been described for the purpose of illustration only and in anon-restrictive manner in any respect. The scope of the presentinvention is defined by the terms of the claims, rather than theembodiments and examples described above, and is intended to include anymodifications within the meaning and scope equivalent to the terms ofthe claims.

REFERENCE SIGNS LIST

1 cutting tool, 1 a rake face, 1 b flank face, 1 c cutting edge portion,10 substrate, 11 AlTiN layer, 11 a first interface, 11 b secondinterface, 11 c central portion of AlTiN layer, 11 d (111) orientedcrystal grains, 12 underlying layer, 13 surface layer, 14 coating, 50CVD apparatus, 52 substrate setting jig, 53 reaction chamber, 54temperature controller, 55 first gas introduction pipe, 56 second gasintroduction pipe, 57 third gas introduction pipe, 58 gas introductionpipe, 59 gas exhaust pipe, 60 gas exhaust port, A imaginary plane A, Bimaginary plane B, C imaginary plane C, D imaginary plane D, E imaginaryplane E, AA boundary line AA, BB boundary line BB, L1 straight line L1,L2 straight line L2, M1 straight line M1, M2 straight line M2

1. A cutting tool including a rake face, a flank face, and a cuttingedge portion connecting the rake face and the flank face together, thecutting tool comprising a substrate and an AlTiN layer provided on thesubstrate, the AlTiN layer including cubic Al_(x)Ti_(1-x)N crystalgrains, an atomic ratio x of Al in the Al_(x)Ti_(1-x)N being 0.7 or moreand less than 0.95, the AlTiN layer including a central portion, thecentral portion being a region sandwiched between an imaginary plane Dand an imaginary plane E, the imaginary plane D being an imaginary planewhich passes through a point 1 μm away in a direction of thickness froma first interface located on a side of the substrate and is parallel tothe first interface, the imaginary plane E being an imaginary planewhich passes through a point 1 μm away from a second interface oppositeto the side of the substrate in the direction of thickness and isparallel to the second interface, the first interface being parallel tothe second interface, when a cross section of the AlTiN layer obtainedwhen cut along a plane including a normal to the second interface at therake face and a normal to the second interface at the flank face issubjected to an electron backscattering diffraction image analysis usinga field emission scanning microscope to determine a crystal orientationof each of the Al_(x)Ti_(1-x)N crystal grains and a color map is createdbased thereon, in the color map, the central portion at the rake facebeing occupied in area at a ratio of 50% or more and less than 80% byAl_(x)Ti_(1-x)N crystal grains having a (111) plane with a normalthereto having a direction within ±15° with respect to the direction ofthe normal to the second interface at the rake face, the central portionat the cutting edge portion being occupied in area at a ratio of 80% ormore by Al_(x)Ti_(1-x)N crystal grains having the (111) plane with anormal thereto having a direction within ±15° with respect to adirection of a normal to the cutting edge portion, the direction of thenormal to the cutting edge portion being a direction of a normal to animaginary plane C including a boundary line on the substrate between therake face and the cutting edge portion and a boundary line on thesubstrate between the flank face and the cutting edge portion.
 2. Thecutting tool according to claim 1, wherein the AlTiN layer has athickness of 2.5 μm or more and 20 μm or less.
 3. The cutting toolaccording to claim 1, further comprising an underlying layer providedbetween the substrate and the AlTiN layer, wherein the underlying layeris composed of a compound consisting of: at least one element selectedfrom the group consisting of a group 4 element, a group 5 element and agroup 6 element of the periodic table and aluminum; and at least oneelement selected from the group consisting of carbon, nitrogen, oxygenand boron.
 4. The cutting tool according to claim 1, further comprisinga surface layer provided on the AlTiN layer, wherein the surface layeris composed of a compound consisting of: at least one element selectedfrom the group consisting of a group 4 element, a group 5 element and agroup 6 element of the periodic table and aluminum; and at least oneelement selected from the group consisting of carbon, nitrogen, oxygenand boron.